The makers of Vita Coco coconut water were slapped with a $5 million-plus suit this morning over charges that their “super-hydrating” beverages aren’t all they’re cracked up to be.

The Manhattan federal court filing says Vita Coco — whose fans include company investors Madonna and Demi Moore, as well as Rihanna, who’s featured in a new ad blitz — falsely claims to have “15 times the electrolytes found in sports drinks.”

The suit cites a recent study by ConsumerLab.com that found “at least some” Vita Coco flavors had “significantly less” sodium and magnesium than advertised.

The suit also alleges that a “confidential witness” has revealed that manufacturer All Market Inc. — which expects to ring up $100 million in sales this year — “knew or should have known of this discrepancy for years.”

“This witness was specifically told that the packaging used and preservatives in Vita Coco products degrade the nutritional contents,” court papers say.

It was filed by Florida lawyer Stacey Fishbein on behalf of anyone who’s purchased the premium-priced beverages — which cost about $2 for an 11-oz. carton — since 2007.

Vita Coco spokesman Arthur Gallego said, “we are confident that Vita Coco continues to be an excellent, all natural source of hydration and that our products’ nutrition labels are accurate and in compliance with the FDA.”

“In fact, Vita Coco coconut water is regularly reviewed by an independent third party to ensure the electrolyte levels stated on our nutritional label are consistent with the amount in our coconut water,” he added.